Purification of liquids containing sugar



Patented Sept. 10, 1929.

GERHARD ELIAS VAN NES, F IASOERGEAN,

JAVA, DUTCH EAST INDIES.

PURIFICATION OF LIQUIDS CONTAINING SUGAR.

No Drawing". Application filed April 30, 1927, Serial No. 188,060, andin the Netherlands September This invention relates to the purificationof sugar-juices obtained from sugar-cane, by means of a base, preferablylime, and carbon-dioxide or other acid gas and has for its object toattain a 'nn'ilicatioii which equals in ell'ect that which can beattained by the carbonation methods at present in use,.without requiringso much lime asis inherent in the known methods.

According to the invention, a quantity of lime or other base is firstadded to the cold raw juice, such that the reaction towardsphenolphthalein is rendered WQakly'alkaline. The solution is thenover-saturated with carbon-dioxide or with other acid gas;

that. is to say, carbon-dioxide, or gases containing carbon-dioxide orother acid gases, are passed through the solution until the latter showsan acid reaction at least towards phenolphthalein. The solution is thenheated to a temperaturenot exceeding 00 (1, preferably a temperature of55 0., and a quantity of lime is added such that the solution shows afinal alkalinity higher than that corresponding to 300 milligrams of CaOper litre in the juice, preferably an alkalinity corresponding to about700 milligrams of CaO per litre when titrated, using phenolphthalein asindicator. This usually requiresabout 10-12 litres of milk of lime of 15Baume per 1000 litres of juice. The precipitate is allowed to settle forabout half an hour. It has been found that when the above mentionedalkalinity and temperature prevail during the settling period, 110

decomposition of reducing sugars occurs, which might be disadvantageousfor the further operations. After 'the precipitate has settled, theturbid juice, having a volume of about 3035% of the total volume of thejuice, is separated from the clear juice by decantation.

The clear juice can be'filtered easily after it has been fullycarbonated, and may then be worked up in the usual manner.

The turbid juice, together with the deposited matter, may be filteredand the filtrate may be added torthe clear juice. As the volume of theturbid juice is relatively very large, however, the filtering operationof this filtering apparatus.

there to juice requires an inconveniently large The turbid uice is resaturated with carbon-dioxide or other acid gas until it is againover.saturated (i. e. acid towards pl enolplithalein) and is then heatedto a temperature above 50 (1.,

preferably to a temperature of 80 (1., and

the precipitate is allowed to settle.

The deposits settle very rapidly. The turbid juice obtained (about 20")can be iiltered very easily. The juice from the filter-press is added tothe clear juice from the liual settling and the liquid obtained in thisway is added to a subsequent batch of cold over-saturated raw juice,operation of heating the latter to before the (1.,

as previously described.

It has been found uice,

liminary treatment saturated raw uice that the addition of which hasbeen subjected to a preas described, to the overhas a favourable inonthe content of lime of the purified juice finally obtained.

What I claim is process of purifying sugar-juices,

comprising the steps of treating the raw juice with lime until it showsa weaklyalkahne reaction, then saturating it with an acid gas until itshows an acid reaction,

heating, the liquid so treated ture not exceeding 00 to a temperaaddinga further quantity of lime until the liquid shows a final sponding to800 mg. uice, and decanting turbid alkalinity higher, than that corre-GaO per liter in the the clear juice from the juice.

process of purifying sugar-juices,

comprising the steps of treating the raw juice with lline until it showsa weaklyalkaline reaction,

then saturating it with carbonic acid gas until it shows an acidreaction, heating temperature not further quantity the liquid so treatedto a. exceeding 00 C., adding a of lime until the liquid shows a finalalkalinity of about 700 mg.

CaO

clear uice from the turbid juice,

er liter in the juice, decanting the saturating the clear juice withcarbonic acid gas, and filtering.

3. A process according to claim 2, in

which the turbid juice is treated with carbonic acid gas until its showsan acid reaction, then heated to a temperature of about 80 C., theprecipitate then allowed to settle, and then decanted and filtered,whereupon the filtered liquid is added, with the clear juice, to afurther batch of raw juice.

- 4. A process of purifying sugar-juices, comprising the steps ofheating the juice to a. temperaturenot exceeding 60 C., treating it withlime to obtain an alkalinity higher than that corresponding to 300 mg.0210 per liter in the juice, allowing the liquid so treated to settle,decanting the clear juice from the turbid juice, treating the turbidjuice with an acid gas until it shows an acid reaction, then heating itto a temperature between 50 (1., and the boiling point at atmosphericpressure, allowing the precipitate to settle, then decanting andfiltering the turbid juice and then adding the filtered liquid, with theclear juice from the last decantation, to a further batch of raw juice.In testimony whereof I aflix mysignature.

GERHARD ELIAS VAN NES.

